Facial injury: a review of biomechanical studies and test procedures for facial injury assessment

The incidence and patterns of maxillofacial fractures and associated head and neck injuries

The aim of this study was to evaluate the incidence and patterns of maxillofacial fractures and the demographic characteristics of associated head and neck injuries. This single-center retrospective cohort study was conducted at the Department of Oral and Maxillofacial Surgery of King Abdullah University Hospital (KAUH) in Irbid, northern Jordan. The data was obtained from the electronic clinical records of all patients in whom maxillofacial fractures and associated head and neck injuries were confirmed. During the five-year period captured by this retrospective study, 481 patients with 1026 maxillofacial fractures (equivalent to 2.13 fractures per patient) were treated. The sample comprised of 369 (76.7%) males and 112 (23.3%) females, resulting in a male/female ratio of 3.3:1. Majority of the patients were in the 21-30 age group and RTA was the most common cause of maxillofacial fractures, accounting for 299 (62.1%) of the analyzed cases. In 316 cases, maxillary fractures were accompanied by associated injuries, 132 (41.77%) of which were intracranial lesions, 80 (25.32%) were skull fractures, and 59 (18.67%) were cervical spine injuries. Based on the obtained data, it can be concluded that the high occurrence of RTA emphasizes the significance of adhering to traffic laws and regulations, as individuals who have suffered serious head and neck injuries as a result of maxillofacial trauma may experience potentially fatal consequences. Thus, management for patients with maxillofacial fractures and concomitant traumas should be multidisciplinary and coordinated.

Does the type of craniomaxillofacial fracture (CMF) differ between patients with intracranial hemorrhage (ICH) and those with blunt cerebrovascular injury (BCVI)? A retrospective study

The purpose of the present study was to investigate and compare craniomaxillofacial fracture (CMF) type in patients with intracranial hemorrhage (ICH) versus blunt cerebrovascular injury (BCVI). A retrospective cohort study was performed. The predictor variables were the types of CMF. The primary outcomes variables were ICH and BCVI. Secondary outcomes were death and survival with or without neurological sequelae. Descriptive, bivariate, and multiple logistic regression statistics were computed, and the significance level was set at P ≤ 0.05. The sample was composed of 1440 patients with a mean age of 46.6 years ±24 years, and 71% were men. Pure orbital wall (odds ratio [OR]), 3.62; 95% confidence interval [CI], 1.32-12.69; P < 0.022), Le Fort III (OR, 16.08; 95% CI, 5.89-43.50; P < 0.001), cranial vault (OR, 9.74; 95% CI, 3.83.24.32; P < 0.001), skull base (OR, 9.42; 95% CI, 3.86-24.02; P < 0.001) and cervical fractures (OR, 5.50; 95% CI, 1.65-15.97; P = 0.003) were significantly associated with BCVI. All of the CMFs (P < 0.001), except for Le Fort I (OR, 0.79; 95% CI, 0.18-2.63; P = 0.731), nasal (OR, 1.05; 95% CI, 0.77-1.42; P = 0.758), and mandibular (OR, 0.68; 95% CI, 0.45-1.01; P = 0.066) fractures, were significantly associated with ICH. Secondary outcomes were negatively influenced by ICH and BCVI (P < 0.001). Within the limitations of the study it seems that Le Fort I and nasal fractures could be protective of cerebrovascular injuries, by cushioning impact forces. On the other hand it seems that patients with pure orbital wall, Le Fort III and cranio-cervical fractures are more prone to having concomitant life-threatening cerebrovascular injuries. This category of patients should have an immediate and comprehensive neurological assessment and CT angiography to rule out BCVI and to determine its severity.

Evaluation of full-face, open-face, and airbag-equipped helmets for facial impact protection

OBJECTIVE

Two-wheeler riders frequently sustain injuries to the head and face in real-world crashes, including traumatic brain injury, basilar skull fracture, and facial fracture. Different types of helmets exist today, which are recognized as preventing head injuries in general; however, their efficacy and limitations in facial impact protection are underexplored. Biofidelic surrogate test devices and assessment criteria are lacking in current helmet standards. This study addresses these gaps by applying a new, more biofidelic test method to evaluate conventional full-face helmets and a novel airbag-equipped helmet design. Ultimately, this study aims to contribute to better helmet design and testing standards.

METHODS

Facial impact tests at two locations, mid-face and lower face, were conducted with a complete THOR dummy. Forces applied to the face and at the junction of the head and neck were measured. Brain strain was predicted by a finite element head model taking both linear and rotational head kinematics as input. Four helmet types were evaluated: full-face motorcycle and bike helmets, a novel design called a face airbag (an inflatable structure integrated into an open-face motorcycle helmet), and an open-face motorcycle helmet. The unpaired, two-sided student's t-test was performed between the open-face helmet and the others, which featured face-protective designs.

RESULTS

A substantial reduction in brain strain and facial forces was found with the full-face motorcycle helmet and face airbag. Upper neck tensile forces increased slightly with both full-face motorcycle (14.4%, p >.05) and bike helmets (21.7%, p =.039). The full-face bike helmet reduced the brain strain and facial forces for lower-face impacts, but not for mid-face impacts. The motorcycle helmet reduced mid-face impact forces while slightly increasing forces in the lower face.

SIGNIFICANCE OF RESULTS

The chin guards of full-face helmets and the face airbag protect by reducing facial load and brain strain for lower face impact; however, the full-face helmets' influence on neck tension and increased risk for basilar skull fracture need further investigation. The motorcycle helmet's visor re-directed mid-face impact forces to the forehead and lower face via the helmet's upper rim and chin guard: a thus-far undescribed protective mechanism. Given the significance of the visor for facial protection, an impact test procedure should be included in helmet standards, and the use of helmet visors promoted. A simplified, yet biofidelic, facial impact test method should be included in future helmet standards to ensure a minimum level of protection performance.

Are Facial Soft Tissue Injury Patterns Associated With Facial Bone Fractures Following Motorcycle-Related Accident?

PURPOSE

The unprotected nature of motorcycle riding exposes motorcyclists to an elevated risk of sustaining facial soft tissue injuries (STIs); however, its link with underlying facial bone fractures remains unexplored. The purpose of this study is to determine whether the type and site of STI sustained by motorcyclists were associated with the presence of underlying facial bone fractures.

MATERIALS AND METHODS

This was a retrospective cohort study of patients identified from the Oral and Maxillofacial Surgery Department of Universiti Kebangsaan Malaysia Medical Center trauma census who had motorcycle-related injury and met the inclusion criteria. The primary predictor variable was the type (laceration, contusion, abrasion, and no injuries) and site of STIs sustained. The site of the facial STI was categorized as per 17 different zones based upon the modified MCFONTZL classification. The primary outcome variable was the presence or absence of facial bone fractures as determined from the computed tomography scan. Descriptive and bivariate statistics were computed to measure the association between sustaining facial bone fractures and type/site of STI.

RESULTS

Seventy three patients (65 men and 8 women) were included in this study. The average age was 31.9 years (standard deviation ± 13.6) with a range of 18 to 70 years. There were 1,241 facial zones being assessed with 285 (23%) and 214 (17%) zones having STI and fractures, respectively. Laceration (124/285, 43%) and the orbital zone (53/285, 19%) were the most common type and site of STI, respectively, among motorcyclists. Facial bone fractures are more commonly seen following STI in the midface (71% of STI had fractures) compared to upper face (53%) and lower face (31%). Sustaining laceration type of STI was not associated with a higher rate of facial bone fracture when compared with other type of STI (54.8% vs 55.9%, P = .858) with the exception of laceration in the frontal zone (42.9% vs 10.5%, P = .022).

CONCLUSIONS

The different types of STI in the facial area cannot be used as a predictor for sustaining underlying facial bone fractures.

Crash test-based assessment of injury risks for adults and children when colliding with personal mobility devices and service robots

Autonomous mobility devices such as transport, cleaning, and delivery robots, hold a massive economic and social benefit. However, their deployment should not endanger bystanders, particularly vulnerable populations such as children and older adults who are inherently smaller and fragile. This study compared the risks faced by different pedestrian categories and determined risks through crash testing involving a service robot hitting an adult and a child dummy. Results of collisions at 3.1 m/s (11.1 km/h/6.9 mph) showed risks of serious head (14%), neck (20%), and chest (50%) injuries in children, and tibia fracture (33%) in adults. Furthermore, secondary impact analysis resulted in both populations at risk of severe head injuries, namely, from falling to the ground. Our data and simulations show mitigation strategies for reducing impact injury risks below 5% by either lowering the differential speed at impact below 1.5 m/s (5.4 km/h/3.3 mph) or through the usage of absorbent materials. The results presented herein may influence the design of controllers, sensing awareness, and assessment methods for robots and small vehicles standardization, as well as, policymaking and regulations for the speed, design, and usage of these devices in populated areas.

Detection and Referral of Orbital and Ocular Injuries Associated With Intimate Partner Violence Following an Educational and Screening Initiative in an Emergency Department

Importance

Intimate partner violence (IPV) is a substantial cause of morbidity and mortality in the US. Previous studies indicate gaps in identifying and referring female patients with IPV-associated orbital and ocular injuries to ancillary services.

Objective

To determine the number of IPV-associated orbital floor fractures, zygomaticomaxillary complex (ZMC) fractures, and ruptured globes referred to ancillary services in adult female patients following an educational and screening intervention to health care professionals.

Design, Setting, and Participants

This single-center retrospective quality improvement analysis examined electronic medical records of adult female patients seen in a single level 1 trauma center emergency department and ophthalmology clinic between January 2015 and February 2019, after the initiative began. Female adults who sustained orbital floor fractures, ZMC fractures, or ruptured globes were included. Preinitiative data were previously collected between January 1995 and January 2015 on adult female patients and published. Data analysis for this study occurred from May 2020 to September 2020.

Interventions

A 2-part, ongoing initiative began January 2015. First, enhancement of IPV screening protocols in the emergency department was conducted. Second, an educational campaign on IPV injury patterns was presented to residents and faculty in ophthalmology, emergency, otolaryngology, and trauma departments.

Main Outcomes and Measures

Comparison of ancillary service involvement preinitiative (January 1995 to January 2015) and postinitiative (January 2015 to February 2019).

Results

A total of 216 adult female patients (mean [SD] age, 55.0 [22.7] years; age range, 18-99 years) sustained orbital floor or ZMC fractures postinitiative. A total of 22 of 216 (10.2%) sustained fractures from IPV compared with 31 of 405 (7.6%) preinitiative (95% CI, -2.2% to 7.3%; P = .28). Documented social work referrals (11 of 31 preinitiative vs 20 of 22 postinitiative; difference, 55% [95% CI, 35%-76%]; P < .001), homegoing safety assessments (1 of 31 preinitiative vs 18 of 22 postinitiative; difference, 79% [95% CI, 61%-96%]; P < .001), and law enforcement involvement (7 of 21 preinitiative vs 16 of 22 postinitiative; difference, 50% [95% CI, 26%-74%]; P < .001) were higher in patients who presented after the initiative with orbital floor and ZMC fractures. A total of 51 adult female patients (mean [SD] age, 57.7 [20.8] years; age range 20-93 years) sustained ruptured globes postinitiative. A total of 5 of 51 patients (9.8%) sustained injury due to IPV postinitiative, compared with 5 of 141 (3.5%) preinitiative (95% patients, -2.5% to 15.0%; P = .08).

Conclusions and Relevance

Following the start of the initiative, referral patterns of adult female patients with IPV-associated orbital fractures improved. Targeted IPV screening of patients with orbital and ocular injuries is essential for effective intervention.

Association between pre- and intraorbital soft tissue volumes and the risk of orbital blowout fractures using CT-based volumetric measurements

Orbital blowout fractures result from trauma which breaks the bony orbital wall while sparing the rim. Previous research into fracture mechanism has focused on bony anatomy. This study evaluates the role of preorbital and intraorbital soft tissue volume in fracture risk. A retrospective case-control study was conducted on 51 cases of adults with unilateral orbital blowout fracture, matched to 51 controls who had experienced orbital trauma by comparable mechanisms without sustaining a fracture. Axial Computed Tomography (CT) images with orbital fine cuts were assessed on a 3D post-processing workstation to measure the volume of the pre- and intraorbital soft tissues, then compared between the two groups using Mann-Whitney U analysis. In the case group, there were 40 males (78%), injured by assault (66%), fall (12%), motor vehicle collision (10%), or other cause (12%). The control group included 33 males (65%), injured by assault (55%), fall (22%), motor vehicle (4%), or other cause (20%). There was no significant difference in mechanism rates between case and control groups. Median preorbital volumes were 12.5 cm³ in the case group and14.1 cm³ in controls (p = 0.02). Median intraorbital volumes were 24.4 cm³ in the case group and 25.9 cm³ in controls (p = 0.003). CT volumetric analysis shows that patients who sustained blowout fractures have lower preorbital and intraorbital soft tissue volume than those who did not fracture. This underscores the significant role that soft tissues play in dissipating impact forces, both anterior to the orbital rim and within the orbit itself.

The Correlation of Age and Patterns of Maxillofacial Bone Fractures and Severity of Associated Injuries Caused by Motorcycle Accidents

BACKGROUND

Every year, there are significant numbers of motorcycle accident casualties in Taiwan. These accidents are the leading cause of maxillofacial trauma. Age should be an important factor of maxillofacial fracture patterns yet there is limited literature on the topic. Therefore, this study aims to evaluate the correlation of age with maxillofacial fracture in motorcycle accidents.

METHODS

This is a retrospective descriptive analysis conducted over 2-year period at Linkou Chang Gung Memorial Hospital. We focused on the population of maxillofacial injury caused by motorcycle accidents. Data, including demographics, age, fracture patterns of facial bones, and other associated injuries, were collected.

RESULTS

Among 881 admissions, there were 179 patients in the minor group, 644 patients in the adult group, and 58 patients in the geriatric group. With patterns of maxillofacial fracture, midface fracture was the most common type. The minor group had higher incidence of mandibular fracture. The geriatric group sustained more midface fracture. Associated injuries, such as severe head injuries and c-spine injury, were more likely to occur with the old age victims. The overall mortality rate was 3.1%.

CONCLUSIONS

Our study presents the different trends of fracture patterns in different age groups, which is associated with different types of treatment required. We summarized all these data in the hope of providing further assistance to trauma doctor dealing with motorcycle accidents.

Associated Injuries in Maxillofacial Trauma: A Study in a Tertiary Hospital in South India

Aim

Maxillofacial trauma when associated with concomitant injuries has a significant potential for increased morbidity. This study aims to identify the causes of trauma, evaluate the types of associated injuries and to highlight the significance of multi professional collaboration in sequencing of treatment.

Patients and Methods

A total of 300 patients who reported to the casualty of a tertiary Hospital in Karnataka with facial fractures were enrolled.

Results

Associated injuries were sustained by 162 patients. The predominant aetiology was the Road Traffic Accident with maximum number of patients in the age group of 20-29 and a male to female ratio of 10.1:1. The mandible was the most frequently fractured bone. Head injury was the most common associated injury. The mortality rate was 0.66%. The mean ISS and GCS values among the patients who sustained associated injuries along with maxillofacial trauma were higher and lower respectively, as compared to those without associated injuries with a statistically significant difference (p < 0.001).

Conclusion

Implementation of strict road safety measures in the rural and interior regions of South India, to prevent morbidity and mortality due to road traffic accidents is essential. Injuries to the facial skeleton must be approached with the knowledge of probable associated injuries that could have been incurred.

Diagnostic reliability of low dose multidetector CT and cone beam CT in maxillofacial trauma-an experimental blinded and randomized study

OBJECTIVES

To assess the diagnostic reliability of low dose multidetector CT (MDCT) and cone beam CT (CBCT) for zygomaticomaxillary fracture diagnosis.

METHODS

Unilateral zygomaticomaxillary fractures were inflicted on four out of six fresh frozen human cadaver head specimens. All specimens were scanned using four MDCT and two CBCT imaging protocols of which the radiation exposure was systematically reduced. A blinded diagnostic routine was simulated at which 16 radiologists and 8 oral and maxillofacial (OMF) surgeons performed randomized image assessments. We considered the findings during an open operative approach of the zygomatic region as the gold standard.

RESULTS

Zygomaticomaxillary fractures were correctly diagnosed in 90.3% (n = 130) of the image assessments. The zygomatic arch was most often correctly diagnosed (91.0%). The zygomatic alveolar crest showed the lowest degree of correct diagnosis (65.3%). Dose reduction did not significantly affect the objective visualization of fractures of the zygomaticomaxillary complex. The sensitivity and specificity also remained consistent among the low dose scan protocols. Dose reduction did not decrease the ability to assess dislocation, comminution, orbital volume, volume rendering and soft tissues. OMF surgeons considered the low dose protocols sufficient for treatment planning.

CONCLUSIONS

Dose reduction did not decrease the diagnostic reliability of MDCT and CBCT for the diagnosis of zygomaticomaxillary fractures.

Functional and Psychological Impact of Nasal Bone Fractures Sustained during Sports Activities: A Survey of 87 Patients

Nasal bone fractures that require reduction are a common sequela of sports injuries. We conducted a survey to ascertain the outcomes of patients who had experienced a nasal bone fracture and who subsequently underwent manipulation under anesthesia. We reviewed data on 217 nasal bone fractures that had been seen at our institution over a 3-year period. Of these, 133 (61.3%) had occurred as a result of a sports activity. Thirty of the 133 patients (22.6%) had been managed conservatively, while the other 103 (77.4%) had undergone manipulation under anesthesia. We were able to contact 87 of the 103 patients (84.5%) by telephone, who served as the study population. The most common sports associated with these 87 injuries were hurling (n = 26; 29.9%), rugby (n = 22; 25.3%), Gaelic football (n =20; 23.0%), and soccer (n = 13; 14.9%). Patients who had undergone treatment within 2 weeks were significantly more satisfied with their outcome than were those who had been treated later (p < 0.01). Twenty-six patients (29.9%) reported that their injury had had a detrimental impact on their subsequent performance in their sport; 12 (13.8%) described a fear of reinjury when they returned to play, 7 (8.0%) experienced functional problems, 3 (3.4%) complained of diminished performance, and 4 others (4.6%) quit playing contact sports altogether. To the best of our knowledge, our study is the first to demonstrate that a fracture of the nasal bones may have a notable psychological impact on an athlete and that it can lead to diminished performance or a complete withdrawal from contact sports.

The facial skeleton: Armor to the brain?

BACKGROUND

With the development of urban setting worldwide, the major issue of concern is the increase in the mortality rate in the population due to road traffic accidents. The face, being the most exposed region is susceptible to injuries and maybe associated with injuries to the adjacent neuro-cranium. The literature has conflicting views on the relationship between facial fractures and head injuries with some authors opining that the facial skeleton cushions the brain while some other authors claim that the facial fractures act as indicators for head injuries.

OBJECTIVES

To analyze the correlation between the facial fractures and head injuries and to assess if the facial skeleton acts to protect the brain from injury.

PATIENTS AND METHODS

A prospective study that included patients who reported to the emergency department of Basaveswar Teaching and General Hospital, Gulbarga, during 2 years, between August 2013 and July 2015 was conducted. A total of 100 patients with facial fractures were enrolled in the study.

RESULTS

Head injuries were sustained by 51 patients in the study. Maximum number of patients was in the age group of 20-29 with a male to female ratio of 10.1:1. The mandible was the most frequently fractured bone in the facial skeleton followed by the zygomatico-maxillary complex. A majority (96%) of patients with head injuries had fractures of either the upper third or the middle third of the face. Contusions and pneumocephalus were the most common head injury encountered. The Glasgow Coma Scale score was significantly lower in patients with associated head injuries as compared to those patients with facial trauma alone. The mortality rate in the study was 2% with both the victims having sustained middle third and upper third fractures respectively with associated head injuries.

CONCLUSION

The facial skeleton does not act to cushion the brain from injury but, in fact, the facial trauma victims should be considered potential head injury patients.

The Le Fort system revisited: Trauma velocity predicts the path of Le Fort I fractures through the lateral buttress

OBJECTIVE

To examine the effect of trauma velocity on the pattern of Le Fort I facial fractures.

METHOD

A retrospective medical record review was conducted on a consecutive cohort of craniofacial traumas surgically treated by a single surgeon between 2007 and 2011 (n=150). Of these cases, 39 Le Fort fractures were identified. Patient demographic information, method of trauma and velocity of impact were reviewed for these cases. Velocity of impact was expressed categorically as either 'high' or 'low': high-velocity fractures were those caused by a fall from >1 story or a motor vehicle collision; low-velocity fractures were the result of assaults with a blunt weapon, closed fist or falls from standing height. The vertical position of each fracture was measured at its point of entry on the lateral buttress and its point of exit on the piriform aperture. To allow for comparison across individuals, values were expressed as ratios based on their location on the face relative to these landmarks. A Wilcoxon rank-sum test was used to compare the fracture heights caused by high- and low-velocity trauma.

RESULTS

The results revealed that high-velocity traumas to the face create Le Fort I fractures at a higher point in the lateral buttress compared with low-velocity traumas. There was no difference between heights at the piriform aperture.

CONCLUSION

High-velocity trauma resulted in higher Le Fort I fracture patterns compared with low-velocity trauma.

The Le Fort system revisited: Trauma velocity predicts the path of Le Fort I fractures through the lateral buttress

Objective

To examine the effect of trauma velocity on the pattern of Le Fort I facial fractures.

Method

A retrospective medical record review was conducted on a consecutive cohort of craniofacial traumas surgically treated by a single surgeon between 2007 and 2011 (n=150). Of these cases, 39 Le Fort fractures were identified. Patient demographic information, method of trauma and velocity of impact were reviewed for these cases. Velocity of impact was expressed categorically as either ‘high’ or ‘low’: high-velocity fractures were those caused by a fall from >1 story or a motor vehicle collision; low-velocity fractures were the result of assaults with a blunt weapon, closed fist or falls from standing height. The vertical position of each fracture was measured at its point of entry on the lateral buttress and its point of exit on the piriform aperture. To allow for comparison across individuals, values were expressed as ratios based on their location on the face relative to these landmarks. A Wilcoxon rank-sum test was used to compare the fracture heights caused by high- and low-velocity trauma.

Results

The results revealed that high-velocity traumas to the face create Le Fort I fractures at a higher point in the lateral buttress compared with low-velocity traumas. There was no difference between heights at the piriform aperture.

Conclusion

High-velocity trauma resulted in higher Le Fort I fracture patterns compared with low-velocity trauma.

Traumatic head injuries in patients with maxillofacial fractures: a retrospective case-control study

OBJECTIVES

To analyse and evaluate the correlation between traumatic head injuries (THIs) and maxillofacial fractures (MF). Age, gender and trauma mechanism correlated with THI were also investigated.

PATIENTS AND METHODS

We conducted a hospital-based retrospective case-control study at Stomatology College and Hospital, Wuhan University. From January 2000 to December 2009, a total of 1131 patients with MF were enrolled in the statistical study to evaluate the association of THI and other risk factors with MF. Among these patients, 86 presented with THI. We utilized binary logistic regression and risk analysis to investigate the associations among MF and other risk factors with HI.

RESULTS

Head injuries (103 injuries) were sustained by 86 patients (7.6%), with male-to-female ratio of 4.1:1.0. Most of the patients (52 patients, 50.5%) also exhibited cranial bone fractures. The age group with most patients was the 30-39 years age group (26 patients, 30.2%), followed by the 19-29 years age group (22 patients, 25.6%). Motor vehicle accident (MVA) was the most common mechanism of injury (49 patients, 74.1%). Patients older than 50 years showed the highest risk for head injury (OR, 2.0; 95% confidence interval, 1.1-3.7; P = 0.025). MVA had a sixfold risk of head injury (OR, 6.2; 95% confidence interval, 1.5-26.1; P = 0.013). Head injuries were more prone to occur in patients who had combined fracture of the mid-face and mandible (OR = 4.6, P < 0.001), and only a 0.3-fold risk of multimandible fractures (P < 0.001), 0.5-fold risk of single mandibular fracture (P = 0.017) and 0.3-fold risk of patients who sustained only single mandibular condylar fracture (P = 0.019).

CONCLUSIONS

The occurrence of head injuries is significantly related to age, aetiology and the pattern and position of maxillofacial fractures.

Significance of osteoporosis in facial bone density using computed tomography

OBJECTIVES

The objectives of this study were to compare the variations of bone density in the midfacial bones as measured by computed tomography (CT) scans between the osteoporosis and control groups and to evaluate the regions that facial trauma and iatrogenic problem often occur in the midface.

METHODS

The 96 patients who underwent both osteomeatal unit CT scans and dual-energy x-ray absorptiometry at our hospital were included in this study retrospectively. Seven skeletal regions were chosen for evaluation: group A (orbital floor, nasal bone), group B (zygomaticomaxillary suture, zygomatic arch, zygomaticofrontal suture), and group C (anterior wall of the maxillary sinus, maxillary process). Forty-seven patients were in the osteoporosis group, and 49 patients were in the control group. On a PACS (picture archiving communication system), the region of interest was analyzed, and the Hounsfield units were measured.

RESULTS

There was a significant difference in the mean bone density of the midfacial bones between the osteoporosis group and the control group (P < 0.01). For both groups, each of comparison of the 7 skeletal regions was greater as group A < group B < group C in this order (P < 0.01).

CONCLUSIONS

We can see the independent effects of osteoporosis on the midfacial bones using CT scans. Estimated Hounsfield unit through CT scan is able to explain osteoporosis, which may be useful in the clinical fields in the future.

The use of combined thermal/pressure polyvinylidene fluoride film airflow sensor in polysomnography

BACKGROUND

The technologies recommended by the American Academy of Sleep Medicine (AASM) to monitor airflow in polysomnography (PSG) include the simultaneous monitoring of two physical variables: air temperature (for thermal airflow) and air pressure (for nasal pressure). To comply with airflow monitoring standards in the sleep lab setting thus often requires the patient to wear two sensors under the nose during testing. We hypothesized that a single combined thermal/pressure sensor using polyvinylidene fluoride (PVDF) film responsive to both airflow temperature and pressure would be effective in documenting abnormal breathing events during sleep.

METHODS

Sixty patients undergoing routine PSG testing to rule out obstructive sleep apnea at two different sleep laboratories were asked to wear a third PVDF airflow sensor in addition to the traditional thermal sensor and pressure sensor. Apnea and hypopnea events were scored by the sleep lab technologists using the AASM guidelines (CMS option) using the thermal sensor for apnea and the pressure sensor for hypopnea (scorer 1). The digital PSG data were also forwarded to an outside registered polysomnographic technologist for scoring of respiratory events detected in the PVDF airflow channels (scorer 2).

RESULTS

The Pearson correlation coefficient, r, between apnea and hypopnea indices obtained using the AASM sensors and the combined PVDF sensor was almost unity for the four calculated indices: apnea-hypopnea index (0.990), obstructive apnea index (0.992), hypopnea index (0.958), and central apnea index (1.0). The slope of the four relationships was virtually unity and the coefficient of determination (r (2)) was also close to 1. The results of intraclass correlation coefficients (>0.95) and Bland-Altman plots also provide excellent agreement between the combined PVDF sensor and the AASM sensors.

CONCLUSION

The indices used to calculate apnea severity obtained with the combined PVDF thermal and pressure sensor were equivalent to those obtained using AASM-recommended sensors.

Assessment of nose protector for sport activities: finite element analysis

There has been a significant increase in the number of facial fractures stemming from sport activities in recent years, with the nasal bone one of the most affected structures. Researchers recommend the use of a nose protector, but there is no standardization regarding the material employed. Clinical experience has demonstrated that a combination of a flexible and rigid layer of ethylene vinyl acetate (EVA) offers both comfort and safety to practitioners of sports. The aim of the present study was the investigation into the stresses generated by the impact of a rigid body on the nasal bone on models with and without an EVA protector. For such, finite element analysis was employed. A craniofacial model was constructed from images obtained through computed tomography. The nose protector was modeled with two layers of EVA (1 mm of rigid EVA over 2 mm of flexible EVA), following the geometry of the soft tissue. Finite element analysis was performed using the LS Dyna program. The bone and rigid EVA were represented as elastic linear material, whereas the soft tissues and flexible EVA were represented as hyperelastic material. The impact from a rigid sphere on the frontal region of the face was simulated with a constant velocity of 20 m s(-1) for 9.1 μs. The model without the protector served as the control. The distribution of maximal stress of the facial bones was recorded. The maximal stress on the nasal bone surpassed the breaking limit of 0.13-0.34 MPa on the model without a protector, while remaining below this limit on the model with the protector. Thus, the nose protector made from both flexible and rigid EVA proved effective at protecting the nasal bones under high-impact conditions.

Should airguns be banned?

In this article, we express concerns regarding the availability of airguns, the injuries that they cause and their abuse as weapons of assault. We wish to stimulate debate on this topic and report a 5-year retrospective analysis of all airgun injuries to the head and neck, presenting to Alder Hey Children's Hospital, Liverpool, from June 1998 to June 2003. We identified 16 patients who suffered such injuries with ages ranging from 5 to 15 years. The majority of cases were violent assaults, which is not in accordance with previous published reports. All of these occurred in public places outside the home. Most incidents occurred through the spring and summer period. Six patients required overnight stay in hospital. Nine patients required operative procedures to remove the airgun pellets. Two patients had serious eye injuries resulting in loss of vision. Two patients had penetrating neck injuries requiring exploration of the wound. The remaining group had either skin-penetrating injuries with lodgement of fragments in subcutaneous tissues or non-skin penetrating injuries. This study highlights serious injuries arising from the abuse of airguns as weapons of assault. Airguns are readily available to people without license. Recent legislation has increased the minimum age at which airguns can be carried in a public place, but we believe that stricter legislation is required to produce a reduction in the number of airgun-related injuries.

Traumatic intracranial haemorrhage in conscious patients with facial fractures--a review of 1959 cases

OBJECTIVE

Facial fracture patients who are conscious with a Glasgow Coma Scale (GCS) score of 15 in the absence of clinical neurological abnormalities are commonly not expected to have suffered severe intracranial pathology. However, high velocity impact may result in intracranial haemorrhage in different compartments.

METHODS

Over a 7-year period, 1959 facial fracture patients with GCS scores of 15 and the absence of neurological abnormalities were analysed. In 54 patients (2.8%) computed tomography scans revealed the presence of accompanying intracranial haemorrhage (study group). These patients were compared with the 1905 patients without intracranial haemorrhage (control group).

RESULTS

Univariate analysis identified accompanying vomiting/nausea and seizures, cervical spine injuries, cranial vault and basal skull fractures to be significantly associated with intracranial bleeding. In multivariate analysis the risk was increased nearly 25-fold if an episode of vomiting/nausea had occurred. Seizures increased the risk of bleeding more than 15-fold. The mean functional outcome of the study group according to the Glasgow Outcome Scale was 4.7+/-0.7.

CONCLUSION

Intracranial haemorrhage cannot be excluded in patients with facial fractures despite a GCS score of 15 and normal findings following neurological examination. Predictors, such as vomiting/nausea or seizures, skull fractures and closed head injuries, enhance the likelihood of an intracranial haemorrhage and have to be considered.

Repair of canine mandibular bone defects with bone marrow stromal cells and porous beta-tricalcium phosphate

Tissue engineering has become a new approach for repairing bone defects. Previous studies have been limited to the use of slow-degradable scaffolds with bone marrow stromal cells (BMSCs) in mandibular reconstruction. In this study, a 30 mm long mandibular segmental defect was repaired by engineered bone graft using osteogenically induced autologous BMSCs seeded on porous beta-tricalcium phosphate (beta-TCP, n=5). The repair of defects was compared with those treated with beta-TCP alone (n=6) or with autologous mandibular segment (n=4). In the BMSCs/beta-TCP group, new bone formation was observed from 4 weeks post-operation, and bony-union was achieved after 32 weeks, which was detected by radiographic and histological examination. In contrast, minimal bone formation with almost fibrous connection was observed in the group treated with beta-TCP alone. More importantly, the engineered bone with BMSCs/beta-TCP achieved a satisfactory biomechanical property in terms of bending load strength, bending displacement, bending stress and Young's modulus at 32 weeks post-operation, which was very close to those of contralateral edentulous mandible and autograft bone (p>0.05). Based on these results, we conclude that engineered bone from osteogenically induced BMSCs and biodegradable beta-TCP can well repair the critical-sized segmental mandibular defects in canines.

Buckling and Hydraulic Mechanisms in Orbital Blowout Fractures

Since the first description of orbital blowout fractures, there has been much confusion as to their etiology. Two principal mechanisms have been proposed to explain their production, the buckling and the hydraulic mechanisms caused, respectively, by trauma to the orbital rim and the globe of the eye. The aim of this study was to evaluate both mechanisms qualitatively and quantitatively. Our protocol used intact cadavers, quantifiable intraocular pressure, variable and quantifiable force, and quantifiable bone strain distribution with strain gauge analysis. One orbit of each cadaver was used to simulate each of the two mechanisms, allowing direct comparison. Fractures produced by the buckling mechanism were limited to the anterior part of the orbital floor, with strain readings reaching up to 3756 microepsilon. Posteriorly, strain did not exceed 221 microepsilon. In contrast, hydraulic-type fractures were much larger, involving anterior and posterior parts of the floor as well as the medial wall of the orbit. Here, strain exceeded 3756 microepsilon in both parts of the floor. Furthermore, we have demonstrated that the average energy required to fracture the orbital floor by the buckling mechanism is 1.54 J, whereas an average energy of 1.22 J is needed to produce this fracture by the hydraulic mechanism. Our results suggest that efforts to establish one or another mechanism as the primary etiology are misplaced. Both mechanisms produce orbital blowout fractures, with different and specific characteristics. We believe this provides the basis for our reclassification of such fractures.

Ballistic Impact to the Forehead, Zygoma, and Mandible: Comparison of Human and Frangible Dummy Face Biomechanics

BACKGROUND

Currently, there is a greater use of nonlethal force in law enforcement and military operations. Because facial injuries have been observed, there is a need to understand the human response to ballistic impacts involving various regions of the face. This study aimed to establish blunt ballistic response corridors for high-speed, low-mass facial impacts to the forehead, zygoma, and mandible, and to determine how these responses compare with those of the frangible Hybrid III headform. Correlation of the human and dummy responses allows injury risk assessment for munitions used in the field.

METHODS

Facial impacts to the forehead, zygoma, and mandible of six cadavers at 42 +/- 10 m/sec were conducted using a 25- to 35-g projectile 37 mm in diameter that was instrumented with an accelerometer to determine impact force. High-speed video analysis determined penetration of the projectile, and autopsy determined the facial fractures. Force and deflection were normalized for the 50% tile response, and corridors were determined for blunt ballistic impacts. Similar tests were conducted on the frangible face of the Hybrid III dummy.

RESULTS

Peak normalized force of 3.5 +/- 0.9 kN on the forehead and 3.0 +/- 1.0 kN on the mandible did not result in fractures, whereas an impact force of 2.3 +/- 0.5 kN on the zygoma caused anterior maxilla fractures. The frangible Hybrid III face developed similar force levels, but with less penetration of the projectile. Its stiffness was 43% greater than that of the cadaver.

CONCLUSIONS

Higher impact force can be tolerated on the forehead and mandible than on the zygoma. Normalized force-deflection and force-time corridors were established for the human response. The frangible Hybrid III face is an effective surrogate for assessing ballistic injury risks, but greater compliance would make it more biofidelic. Initial human tolerance levels of 6.0 kN for the forehead, 1.6 kN for the zygoma, and 1.9 kN for the mandible have been established for ballistic impacts to the face.

Strain gauge biomechanical evaluation of forces in orbital floor fractures

Since the first description of orbital blow-out fractures, there has been much confusion as to their aetiology. Two principal mechanisms have been proposed to explain these fractures, the buckling and hydraulic mechanisms, caused by trauma to the orbital rim and the globe of the eye, respectively. Previous experimental and clinical studies have aimed to support one or other of these two theories. However, these studies have failed to provide quantifiable data to objectively support their conclusions. We present the results of a study of these two proposed mechanisms under identical conditions, using quantifiable intraocular pressure, variable and quantifiable force, and quantifiable bone strain distribution with strain gauge analysis in fresh intact human post-mortem cadavers. Both qualitative and quantitative findings suggest that efforts to establish one theory over the other as the primary mechanism have been misplaced. Both mechanisms produce orbital floor fractures, although these fractures differ fundamentally in their size and location. We have objectively demonstrated that it is easier to fracture the orbital floor by the hydraulic mechanism than by the buckling mechanism, and provided quantitative data for the average force required to displace the orbital floor.

Facial trauma and the risk of intracranial injury in motorcycle riders

STUDY OBJECTIVE

We describe the associations among facial fracture, helmet use, skull fracture, and traumatic brain injury in injured motorcycle riders.

METHODS

The study population consisted of 5,790 motorcycle riders who sustained an injury from a crash in 1991, 1992, or 1993 and were identified from emergency department or hospital records in 28 hospitals in 11 California counties. Diagnostic information was abstracted from ED or hospital records and coded to the 1990 Abbreviated Injury Scale. The risk of traumatic brain injury was examined by using odds ratios and 95% confidence intervals. Logistic regression analysis was used to examine the associations among helmet use, skull fracture, facial fracture, and traumatic brain injury.

RESULTS

Facial injury was diagnosed in 24.4% of all injured riders, including 411 with one or more facial fractures. The odds of traumatic brain injury were 3.5 times greater with than without a facial injury and 6.5 times greater with a facial fracture than with no facial injury. Significantly increased odds of traumatic brain injury were observed for fracture of all bones of the face, but the highest odds of traumatic brain injury were found in riders with fractures to bones of the upper face. Helmet use status and the presence of skull fracture were found to be significant effect modifiers. Facial fracture with concurrent skull fracture increased the risk of traumatic brain injury dramatically. Facial fractures are more strongly associated with traumatic brain injury in helmeted riders.

CONCLUSION

The presence of facial fractures increases the risk of traumatic brain injury. Riders with facial fractures should be screened for brain injury, regardless of helmet use status.

Orbital blowout fractures: experimental evidence for the pure hydraulic theory

BACKGROUND

The mechanism of injury and the underlying biomechanics of orbital blowout fractures remain controversial. The "hydraulic" theory proposes that a generalized increased orbital content pressure results in direct compression and fracturing of the thin orbital bone.

OBJECTIVE

To examine the pure hydraulic mechanism of injury by eliminating the factor of globe-to-wall contact and its possible contribution to fracture thresholds and patterns.

MATERIALS AND METHODS

Five fresh human cadaver specimens were used for the study. In each cadaver head, 1 orbit was prepared to mimic the normal physiologic condition by increasing the hypotony of the cadaver globe to normal intraocular pressure (15-20 mm Hg) with intravitreous injection of isotonic sodium chloride solution (saline). The second orbit served as a "hydraulic control," whereby the globe and orbital contents were exenterated and replaced by a saline-filled balloon at physiologic intraocular pressure. A 1-kg pendulum measuring 2.5 cm in diameter was used to strike the cadaver heads. Drop heights ranged from 0.2 m to 1.1 m (1960 mJ to 10 780 mJ energy). Each head was struck twice, once to each orbit. Direct visualization, high-speed videography, and computed tomographic scans were used to determine injury patterns at various heights between the 2 orbits.

RESULTS

A fracture threshold was found at a drop height of 0.3 m (2940 mJ). Fracture severity and displacement increased with incremental increases in drop height (energy). Fracture displacement, with herniation of orbital contents, was obtained at heights above 0.5 m (4900 mJ). Isolated orbital floor fractures were obtained at lower heights, with medial wall fractures occurring in conjunction with floor fractures at higher energies (> or =6860 mJ). The globe intact side and balloon (hydraulic control) side showed nearly identical fracture patterns and levels of displacement at each drop height.

CONCLUSIONS

This study provides support for the "hydraulic" theory and evidence against the role of direct globe-to-wall contact in the pathogenesis of orbital blowout fractures. In addition, the orbital floor was found to have a lower threshold for fracture than the medial wall. Preliminary threshold values for fracture occurrence and soft tissue displacement were obtained.

An investigation into the mechanism of orbital blowout fractures

For over a century, since the first description of an orbital 'blowout' fracture, there has been debate and confusion regarding the mechanism of production of these fractures. An orbital blowout fracture throughout this paper refers to fractures exhibiting displacement of the orbital floor or walls without an associated fracture of the orbital rim. These are the so called 'pure' blowout fractures as described by Converse. Involvement of the orbit in a variety of facial fracture patterns is easily explained on anatomical grounds. The orbital blowout fracture and symptom complex are readily recognisable but explanation of the mechanisms involved is not easily apparent. Experimental and clinical studies have generally aimed to support one or other of two proposed mechanisms. The 'buckling' theory contends that the fracture is produced as a result of transmission of force to the orbital floor from a blow to the orbital rim (Fig. 1). The 'hydraulic' theory differs in suggesting the force is transmitted to the floor via a direct blow to the globe (Fig. 2). Review of the literature reveals that there are major flaws in the design and execution of previous experimental methods. Most studies have incorporated some or all of the following limitations: low numbers, unquantified forces, non human models, incomplete soft tissues, poor simulation of in vivo conditions and a failure to isolate the position of the striking force. No study has ever provided a direct comparison between the two mechanisms under identical conditions. We present the results of such a study undertaken on 47 fresh cadaver orbits using the same quantifiable force and under the same experimental conditions. The results demonstrate that the efforts to establish either mechanism as the primary aetiology have been misplaced. Both mechanisms produce orbital blowout fractures. The fractures produced, however, are fundamentally different in their size, position and likely clinical significance.

Epidemiologic features of facial injuries among motorcyclists

STUDY OBJECTIVE

To describe the extent, nature, and severity of facial injuries among motorcyclists injured in a crash requiring hospital treatment.

METHODS

The study population consisted of 5,790 motorcycle riders who sustained a nonfatal crash injury during 1991, 1992, or 1993 in 10 California counties. The injured riders were identified in 28 hospitals during 1991 and 1992 and in 18 of these 28 hospitals in 1993. Information was collected from crash reports and hospital records. All injuries were coded according to the 1990 Abbreviated Injury Scale.

RESULTS

Facial injury was present in 24.3% of injured riders, a high proportion of them young men. Among riders wearing helmets, 36.8% had facial injuries, compared with 53.8% of those not wearing helmets. Soft tissue injuries and facial fractures were present in 72% and 22% of the injured, respectively. The maxilla (22%), orbit (16%), and nasal (16%) bones were the most frequently fractured facial bones. The frequency of multiple facial injuries, severity of facial injuries, and incidence of high-severity facial fractures was greater among nonhelmeted riders compared with helmeted riders. Upper facial fractures were more common among riders without helmets compared with those wearing helmets.

CONCLUSION

This study provides evidence of the protective value of helmets to reduce risk of facial injury. Information on the positive effect of facial injury sparing provided by helmet use should be incorporated into helmet promotion programs.